A Phase 1/2 interventional study of ATX-898 and ATX-898 in Advanced Solid Tumors, sponsored by Antares Therapeutics, Inc. Recruiting at 6 sites in 2 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-16.
Sponsored by Antares Therapeutics, Inc · Phase 1/2, Interventional, and Treatment
Study ATX-898-101 is a phase 1/2 open-label study evaluating the safety, tolerability, pharmacokinetic, and preliminary efficacy of ATX-898 as monotherapy and in combination with anti-neoplastic agents in selected solid tumors. This study consists of 2 parts. Part 1 evaluates ATX-898 as monotherapy and Part 2 evaluates ATX-898 in combination with anti-neoplastic agents of interest. Both parts will consists of a dose escalation portion and a dose expansion portion.
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 343 is above the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →This is the only study on the registry with Antares Therapeutics, Inc as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
For Part 1a (monotherapy dose escalation)
For Part 2a (combination dose escalation)
Exclusion Criteria:
Cohort Specific:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Relapsed and refractory
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CTCAE grade
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ATX-898 will be given at a protocol defined starting dose for the treatment of participants with selected advanced or metastatic solid tumors. Subsequent dose regimen will be determined during study execution
Drug: ATX-898
ATX-898 will be given at the recommended dose for expansion (RDE) for the treatment of participants with selected advanced or metastatic ovarian cancer
Drug: ATX-898
ATX-898 will be given at the recommended dose for expansion (RDE) for the treatment of participants with selected advanced or metastatic gynecologic cancers other than ovarian cancers
Drug: ATX-898
ATX-898 will be given at the recommended dose for expansion (RDE) for the treatment of participants with selected advanced or metastatic solid tumors other than gynecologic cancers
Drug: ATX-898
ATX-898 will be given at a recommended starting dose in combination with fulvestrant and abemaciclib both at the protocol defined doses for the treatment of participants with advanced or metastatic HR+HER2- breast cancer. Subsequent dose regimen of ATX-898 will be determined during study execution
Drug: ATX-898
ATX-898 will be given at a recommended dose for expansion (RDE) in combination with fulvestrant and abemaciclib both at the protocol defined doses for the treatment of participants with advanced or metastatic HR+HER2- breast cancer
Drug: ATX-898, fulvestrant, ribociclib
ATX-898 will be given at a recommended dose for expansion (RDE) in combination with fulvestrant and ribociclib both at the protocol defined doses for the treatment of participants with advanced or metastatic HR+HER2- breast cancer
Drug: ATX-898, fulvestrant, ribociclib
ATX-898 will be given at a recommended starting dose in combination with fulvestrant and ribociclib both at the protocol defined doses for the treatment of participants with advanced or metastatic HR+HER2- breast cancer Subsequent dose regimen of ATX-898 will be determined during study execution
Drug: ATX-898, fulvestrant, ribociclib
Doses defined per protocol
RDE
RDE
RDE
Doses defined per protocol
Drug pages: Fulvestrant · Ribociclib
ATX-898 at RDE, Fulvestrant and abemaciclib: doses defined per protocol
Drug pages: Fulvestrant · Ribociclib
ATX-898 at RDE, Fulvestrant and abemaciclib: doses defined per protocol
Drug pages: Fulvestrant · Ribociclib
Doses defined per protocol
This study also gives Abemaciclib. No intervention listed here names it: that was found by reading the record.
Part 1a monotherapy dose escalation - Occurrence of Dose limiting toxicities (DLTs)
Toxicities occurring within the first treatment cycle (28 days). DLTs will be assessed in severity by the investigators per CTCAE v 6.0
Time frame: 12 months
Part 1a monotherapy dose escalation - Maximally tolerated/tested dose (MTD)
Maximum dose deemed safe and well tolerated during dose escalation
Time frame: 12 months
Part 1a monotherapy dose escalation - Recommended dose for expansion (RDE)
Monotherapy dose recommended to test during dose expansion
Time frame: 12 months
Part 1a monotherapy dose escalation - Treatment emergent adverse events (TEAEs)
Any adverse event (AE) either reported for the first time or worsening of a pre-existing event after first dose of study drug.
Time frame: 12 months
Part 1b monotherapy dose expansion - Objective Response Rate (ORR)
Percentage of participants with confirmed CR or PR per RECIST 1.1
Time frame: 24 months
Part 2a combination dose escalation - Occurrence of Dose limiting toxicities (DLTs)
Toxicities occurring within the first treatment cycle of combination therapy (28 days). DLTs will be assessed in severity by the investigators per CTCAE v 6.0
Time frame: 18 months
Part 2a combination dose escalation - Maximally tolerated/tested dose (MTD)
Maximum dose deemed safe and well tolerated during dose escalation of with combination treatment
Time frame: 18 months
Part 2a combination dose escalation - Recommended dose for expansion (RDE)
Recommended dose for expansion (RDE) Monotherapy dose recommended to test during dose expansion of combination treatment 18 months
Time frame: 18 months
Part 2a combination dose escalation - Treatment emergent adverse events (TEAEs)
Any adverse event (AE) either reported for the first time or worsening of a pre-existing event after first dose of study drug. 18 months
Time frame: 18 months
Part 2b combination dose expansion - Objective Response Rate (ORR)
Percentage of participants with confirmed CR or PR per RECIST 1.1
Time frame: 36 months
Part 1a monotherapy dose escalation - Pharmacokinetic assessment Cmax
Cmax of ATX-898 following treatment
Time frame: 12 months
Part 1a monotherapy dose escalation - Pharmacokinetic assessment Tmax
Time it takes for the study drug to reach peak concentration (Cmax) in the blood following treatment
Time frame: 12 Months
Part 1a monotherapy dose escalation - Pharmacokinetic assessment AUC
Area under the conc-time curve exposure of the study drug following treatment
Time frame: 12 Months
Part 1a monotherapy dose escalation - Pharmacokinetic assessment T 1/2
Time required for the concentration of study drug in the body to reduce by half following treatment
Time frame: 12 Months
Part 1a monotherapy dose escalation - Pharmacokinetic assessment Ctrough
Lowest measured concentration of study drug in the blood right before the next scheduled dose
Time frame: 12 Months
Part 1a monotherapy dose escalation - Objective Response Rate (ORR)
Percentage of participants with confirmed CR or PR per RECIST 1.1
Time frame: 12 months
Part 1b monotherapy dose expansion - Treatment emergent adverse events (TEAEs)
Any adverse event (AE) either reported for the first time or worsening of a pre-existing event after first dose of study drug
Time frame: 24 Months
Part 1b monotherapy dose expansion - Pharmacokinetic assessment Cmax
Cmax of ATX-898 following treatment at RDE
Time frame: 12 months
Part 1b monotherapy dose escalation - Pharmacokinetic assessment Tmax
Time it takes for the study drug to reach peak concentration (Cmax) in the blood following treatment at RDE
Time frame: 12 Months
Part 1b monotherapy dose escalation - Pharmacokinetic assessment AUC
Area under the conc-time curve exposure of the study drug following treatment at RDE
Time frame: 12 Months
Part 1b monotherapy dose escalation - Pharmacokinetic assessment T 1/2
Time required for the concentration of study drug in the body to reduce by half following treatment at RDE
Time frame: 12 Months
Part 1b monotherapy dose escalation - Pharmacokinetic assessment Ctrough
Lowest measured concentration of study drug in the blood right before the next scheduled dose at RDE
Time frame: 12 Months
Part 2a combination dose escalation - Objective Response Rate (ORR)
Percentage of participants with confirmed CR or PR per RECIST 1.1
Time frame: 18 months
Part 2a monotherapy dose expansion - Pharmacokinetic assessment Cmax
Cmax of ATX-898 following treatment
Time frame: 12 months
Part 2a monotherapy dose escalation - Pharmacokinetic assessment Tmax
Time it takes for the study drug to reach peak concentration (Cmax) in the blood following treatment
Time frame: 12 Months
Part 2a monotherapy dose escalation - Pharmacokinetic assessment AUC
Area under the conc-time curve exposure of the study drug following treatment
Time frame: 12 Months
Part 2a monotherapy dose escalation - Pharmacokinetic assessment T 1/2
Time required for the concentration of study drug in the body to reduce by half following treatment
Time frame: 12 Months
Part 2a monotherapy dose escalation - Pharmacokinetic assessment Ctrough
Lowest measured concentration of study drug in the blood right before the next scheduled dose
Time frame: 12 Months
Part 2b combination dose expansion - Treatment emergent adverse events (TEAEs)
Any adverse event (AE) either reported for the first time or worsening of a pre-existing event after first dose of study drug when given in combination
Time frame: 36 months
Part 2b monotherapy dose expansion - Pharmacokinetic assessment Cmax
Cmax of ATX-898 following treatment at RDE when given in combination
Time frame: 12 months
Part 2b monotherapy dose escalation - Pharmacokinetic assessment Tmax
Time it takes for the study drug to reach peak concentration (Cmax) in the blood following treatment at RDE when given in combination
Time frame: 12 Months
Part 2b monotherapy dose escalation - Pharmacokinetic assessment AUC
Area under the conc-time curve exposure of the study drug following treatment at RDE when given in combination
Time frame: 12 Months
Part 2b monotherapy dose escalation - Pharmacokinetic assessment T 1/2
Time required for the concentration of study drug in the body to reduce by half following treatment at RDE when given in combination
Time frame: 12 Months
Part 2b monotherapy dose escalation - Pharmacokinetic assessment Ctrough
Lowest measured concentration of study drug in the blood right before the next scheduled dose at RDE when given in combination
Time frame: 12 Months
Plan to share: No — No individual participant data will be shared due to privacy and confidentiality requirements.
No publications or documents are linked to this record.
Started Aug 2026 (actual). Primary completion is estimated for Oct 2029, 37 months after the start.
Of 161 industry-sponsored phase 1/2 interventional studies under Breast Neoplasms, half reached primary completion within 59 months of starting (the median), counting those still running; a quarter within 44 and three quarters within 75. This study's planned 37 months is below that.
Counting every sponsor, half of 327 studies reached it within 61 months; a quarter within 45 and three quarters within 88.
Primary completion moved once since we started tracking on Sep 25, 2026: Oct 2028 → Oct 2029, on Oct 16, 2026.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drugs tested here: Fulvestrant · Ribociclib